If I understand your question, your problem is that you paid for the service for many months, and didn't cancel it. Their argument will be that you had an "implied in fact" contract, based on their conduct of supplying the service and your conduct of knowingly paying for it one month, and thereafter accepting it, so your payment for it is fair.
If you tried to cancel the service and weren't able to, or they billed you for months that you didn't get the service, the answer would be different.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.